Nature loves repeating her designs. Take a look at some of the barren trees in the fall, then at some fan coral, and then at the veins in your hand. They all have a similar branched look. When you have a good design, you reuse it over and over again.
Sometimes, when nature reuses designs, it is creepy. It was creepy/awesome with celosia and it is creepy/awesome with coral:
The bane of zombies everywhere.
Brain coral (family Faviidae) is an animal, yes. Corals are cnidarians, just like anemones, jellyfish, Man-o'-Wars, and hydras. Corals in particular are classified as anthozoans - literally, "flower-animals." They are closely related to sea anemones, and, like them, spend their entire lives in polyp form.
Brain corals in particular are nocturnal feeders. They extend their tentacles at night and feed on anything small passing by. One genus of brain coral, Favia, is semi-aggressive; it will sting other corals with its long tentacles during the night. If that does not sound like a Japanese porno comic to you, you clearly do not know how the Japanese do their porn.
This is your brain on drugs.
A whole head (yes, it is actually called that) of brain coral is formed out of thousands of clones of one individual. When brain corals die, their bodies become the corrugated, calcified structure that gives the coral its name. A single head can get up to two meters high and live for over 900 years. Mind, this is a colony of clones building on top of the dead bodies of their brethren.
Of course, when humans make houses out of bones, it's considered creepy. Hmph. Whippersnappers.